1. Field of the Invention
The present invention generally relates to resin compositions that contain polycarbonate resins having high flame retardancy and can be molded into thin products. In particular, the present invention relates to a flame retardant polycarbonate resin composition containing an environmentally friendly halogen-free flame retardant and a recycled polycarbonate resin recycled from discarded optical disks.
2. Description of the Related Art
Recently, in various fields including electrical and electronic appliances such as home electric and electronic appliances, office automation (OA) equipment, and information and communication appliances, products with mechanical strength are desired under the trends of weight and size reduction. There is also social need for environment-conscious products that do not use halogens. In this regard, plastics commonly used in products in the past such as polystyrene (PS) and acrylonitrile-butadiene-styrene (ABS) resins are being increasingly replaced by polycarbonate (PC) resins that exhibit high strength despite a small thickness. Under such trends, flame retardant PC resins rendered flame retardant by incorporation of phosphorus (phosphates and the like)-based flame retardants are increasingly used.
However, since flame retardant PC resins contain large amounts (several to some ten percent by weight) of phosphorus-based flame retardants, gas may be generated in the course of injection-molding the resin compositions, and the heat resistance, recyclability, and storage stability (in high temperature and high humidity) of the resin compositions may deteriorate significantly. These problems occur because phosphorus-based flame retardants are highly hydrolyzable or pyrolyzable and because the amounts added to the resins are large. To address these problems, Japanese Unexamined Patent Application Publication Nos. 2004-143410 and 2005-54085 propose fabrication of flame retardant PC resins by using a functional group-containing silicone and a combination the functional group-containing silicone and an organic alkali metal salt as the flame retardant (without using a phosphorus-based flame retardant). However, the methods described in the aforementioned documents rarely provide sufficient flame retardancy. The flame retardancy desired for electric home appliances and the like with a small thickness has not been achieved.